Location via Repeater Input

Discussion in 'CB & Scanner Discussion' started by FoxStang, Aug 4, 2018.

  1. InsipidMonkey

    InsipidMonkey Premium Monkey Advanced User Acceptus Premium Member

    Messages:
    3,732
    Likes Received:
    5,701
    Country:
    United States
    Joined:
    Mar 22, 2017
    Location:
    New England
    I'm trying the same thing for a local site. One change I made was to set a wildcard TGID (i0) and/or enable ID Search so that I can pick up any inputs to the repeater, and not just police. Trying to get as much traffic as I can for testing purposes.
     
  2. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
     
  3. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    Score this weekend:

    FoxStang-1
    InsipidMonkey-0

    No hits on encrypted comms yet.

    Posted from my Pixel 2 using the RDF Mobile App!

    Edit: FoxStang-7 thanks to attempted suicide (not to make light of such a serious event) still no encrypted notices.
     
    Last edited: Sep 9, 2018
    FoxStang likes this.
  4. FoxStang

    FoxStang Sly fox, dumb bunny. Advanced User Premium Member

    Messages:
    920
    Likes Received:
    2,210
    Country:
    United States
    Joined:
    Oct 12, 2015
    Location:
    PNW
    Glad you’re seeing results! With so much dispatch information being transmitted to MDT units, I’m finding it to be pretty rare to pick up inputs even when I’m passing right by a cop. I got pretty lucky that first day.
     
  5. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    I'm having the same issue. All the hits were at my house with the action being close by. From my understanding, these radios send out a constant ping to the tower. I assume that's what the CC is looking for. Would that be offset from the CC frequency as well? If so, would the TGID be contained in there?

    Posted from my Pixel 2 using the RDF Mobile App!

    For example; if the CC is 856.6375, would the radios connected to that site send out a constant signal at 811.6375? If they did, would the TGID be contained there as well?
     
    Last edited: Sep 10, 2018
  6. FoxStang

    FoxStang Sly fox, dumb bunny. Advanced User Premium Member

    Messages:
    920
    Likes Received:
    2,210
    Country:
    United States
    Joined:
    Oct 12, 2015
    Location:
    PNW
    Close Call is simply looking for any frequency within the bands you select that rises above a certain strength (-15dBm if I remember right). The only thing I've ever used it for is sticking another radio right next to the scanner and transmitting so that the scanner identifies the frequency of the radio.

    Trying to catch those pings is really difficult for the scanner because of the way it operates, that's what I was mentioning before about it being like a slow radar detector trying to catch the super-quick 16ms POP shots. It would have to coincidentally be on that exact frequency as it scans all of your list, at the exact moment the ping happens.
     
    GTO_04 and InsipidMonkey like this.
  7. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    Sorry, I shouldn't have abbreviated. By CC I meant the control channel.

    Posted from my Pixel 2 using the RDF Mobile App!
     
    GTO_04 and FoxStang like this.
  8. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    Also, that's right! I remember you catching the ping packets sitting across from the SO. So the idea of trying to monitor that for an early alert may be better suited to a SDR?

    Posted from my Pixel 2 using the RDF Mobile App!
     
    InsipidMonkey likes this.
  9. InsipidMonkey

    InsipidMonkey Premium Monkey Advanced User Acceptus Premium Member

    Messages:
    3,732
    Likes Received:
    5,701
    Country:
    United States
    Joined:
    Mar 22, 2017
    Location:
    New England
    Yeah, I was thinking we were looking for actual voice transmissions (encrypted/digital or not) from the radios, not the periodic data packets the radios send when they are associated. I like @FoxStang's analogy of trying to catch 16ms K band POP shots. Comparatively, our scanners are like a sleeping Escort Solo.

    SDR would certainly be better for capturing the data packets, and would make for an interesting "Target BlueEye" like solution. The only downside is the narrow IF bandwidth of typical consumer SDRs, but this could be overcome by using multiple SDRs at the same time. It's a really good idea @dchemist, I will certainly see how far I can get with it when I have time.
     
    GTO_04, Tallyho and dchemist like this.
  10. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    There's some really good SDRs out there but you're right, they are expensive. Thinking about @xydrine idea of a stand alone RDFGS 2.0 type device that is custom made got me to wondering the same about a similar application here. I'm going to have to bite the bullet and order a second Raspberry Pi and learn Linux to work on a proof of concept. I think this may be a years long venture.

    Posted from my Pixel 2 using the RDF Mobile App!
     
    GTO_04 and Tallyho like this.
  11. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    InsipidMonkey likes this.
  12. InsipidMonkey

    InsipidMonkey Premium Monkey Advanced User Acceptus Premium Member

    Messages:
    3,732
    Likes Received:
    5,701
    Country:
    United States
    Joined:
    Mar 22, 2017
    Location:
    New England
    Good find! It looks like you'll still be limited to ~2.4MHz of bandwidth though.

    I picked up a LimeSDR mini from a previous crowdfunding campaign, and need to get that working with my RPi next. It gives you ~20MHz of bandwidth for about $100, along with a more sensitive receiver, TX capability, and on-board FPGA.
     
    dchemist likes this.
  13. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    Dang, nice catch. What are you finding in the 50 MHz bandwidth range? Everything I'm finding is just way too pricey for me to pay. This is one of the cheaper options;

    https://www.mouser.com/ProductDetai...O09HolIzwNflO7MOlr9xv_sCT9qXBGtxoCNi0QAvD_BwE

    Posted from my Pixel 2 using the RDF Mobile App!
     
  14. InsipidMonkey

    InsipidMonkey Premium Monkey Advanced User Acceptus Premium Member

    Messages:
    3,732
    Likes Received:
    5,701
    Country:
    United States
    Joined:
    Mar 22, 2017
    Location:
    New England
    The $299 LimeSDR (non-mini) is capable of ~60 MHz, but you need a pretty beefy processor to support that. I think trying to sample a full 60 MHz of bandwidth is too much to ask of something like the RPi, unless you are really good at leveraging the FPGA to minimize the computational burden.

    Here is a pretty comprehensive list of SDRs and their capabilities: List of software-defined radios - Wikipedia

    And here is an older roundup of SDRs: www.rtl-sdr.com: Roundup of Software Defined Radios
     
  15. mikeoxlong

    mikeoxlong Learning to Fly Beginner User

    Messages:
    61
    Likes Received:
    35
    Country:
    Canada
    Joined:
    Jun 18, 2017
    No, they only transmit when the officer keys the mic, they have data to send, they move into a different coverage area or the system loses track of them.

    By data, I mean GPS or Mobile Work Station or something similar if they are using the trunking system for data. Most use cellular for data though.

    If you use a utility like DSD to watch the control channel, you will see this activity.
     
    GTO_04 likes this.
  16. dchemist

    dchemist Premium Member Intermediate User Premium Member

    Messages:
    584
    Likes Received:
    572
    Country:
    United States
    Joined:
    Jul 26, 2017
    Location:
    Benton, AR
    Gotcha, thanks. I'm trying to brainstorm some constant RF that we could look for but kinda coming up short.

    I did notice that the SO vehicles are broadcasting WiFi (assume LTE like you started) but I think it's been discussed that that isn't going to be a workable solution based on all the other LTE devices out there.

    Posted from my Pixel 2 using the RDF Mobile App!
    --- Double Post Merged, Sep 17, 2018 at 3:23 PM, Original Post Date: Sep 11, 2018 ---
    So to follow up, I don't believe either the InsipidMonkey or FoxStang methods will work for encrypted systems. I am receiving alerts on both conventional and trunking systems but nothing from encrypted systems. To be fair, I believe it is more to do with the BCDx36HP skipping over the encrypted TGs and I'm really not sure there is a way around this. Users of other radios may have more luck.
     
    Tallyho likes this.
  17. GTO_04

    GTO_04 Premium Member Advanced User Premium Member

    Messages:
    3,755
    Likes Received:
    3,240
    Country:
    United States
    Joined:
    May 21, 2011
    My 396XT will not pass encrypted audio, but it WILL pause on ENC talkgroups and display the TG ID or alpha tag if I have set one. Can't you program your X36 to sound an audio alert (beep) when it stops on an encrypted TG? I have that ability with mine and it is not as sophisticated as a 436 or 536.

    GTO_04
     
    Last edited: Sep 17, 2018 at 4:07 PM
  18. FoxStang

    FoxStang Sly fox, dumb bunny. Advanced User Premium Member

    Messages:
    920
    Likes Received:
    2,210
    Country:
    United States
    Joined:
    Oct 12, 2015
    Location:
    PNW
    That might be the issue; I don't recall seeing any options relating to encryption, it may have been one of those things where Uniden engineers said "Why in the world would anyone ever want this" and removed that capability to simplify the product since they were adding new features.
     
    GTO_04 likes this.